"One thing I've found about toilets, (and I've had a lot of the
cheap Jabsco's) is they don't seem to suck
water in well if they have a vented loop in the intake.. often gurgling lot. anyone else have this issue? Is this the OP's complaint?"
Cheechako, You shouldn't put a vent in an intake line unless there is a way to close it when you operate the
toilet. They are designed to let air into the line which makes it very hard to generate suction in the line.
Electric toilets usually come with a solenoid operated vent that closes when the
toilet flushes.
Jabsco Solenoid Valve Kit, 37016-2000
Most manual toilets have a hose connecting the
pump to the back of the bowl. You can extend that hose and install a vented loop in it. It's a pressure line not a suction line.
If the vented loop in your intake line is within reach, just cover the hole with your finger while you
work the
pump.